The present invention relates generally to a valve unit, and in particular, a valve unit disposed in an ink supply channel for use in connecting an ink-jet recording head and an ink tank, and which is capable of generating a negative pressure.
Conventional inkjet printers generally include a carriage which is loaded with an inkjet recording head and an ink cartridge for supplying ink. With the carriage in place, the carriage reciprocately moves along a recording paper and discharges ink drops onto recording paper according to printing data. The recording head discharges the ink drops from nozzle holes by generating a pressure within a pressure generating chamber. The pressure generating chamber communicates with a common ink chamber and the nozzle holes of the recording head.
With such a recording head, since the nozzle hole is normally positioned lower than the ink liquid level in the ink cartridge, the head pressure acts on the nozzle hole and causes the ink to leak out of the nozzle hole. In order to solve this problem, a porous material is usually placed in the ink cartridge, so that the capillary force from the porous material keeps the ink pressure in the ink cartridge slightly lower than the pressure in the recording head.
When the quantity of the ink absorbed into the porous material decreases as ink use increases the capillary force of the porous material delays the supply of ink into the recording head. As a result, the ink in the carriage is not completely used. Another problem associated with the ink carriage is the large size of the ink cartridge required to house the large volume of the porous material.
Generally an ink cartridge is constructed such that a wall having an opening is provided in the lower portion of an ink tank thus dividing the lower portion thereof into an ink reservoir and a cavity. A check valve is installed in the opening of the wall, such that when ink pressure in the recording head is lowered the valve opens, discharges the ink from the reservoir into the cavity and supplies the ink to the recording head.
Accordingly, it is desirable to provide an ink cartridge for an ink-jet recording head, which overcomes the inadequacies of the prior art.
Generally speaking, in accordance with the invention an ink cartridge for an ink-jet recording head is constructed such that, a diaphragm valve comprising an elastic diaphragm having an opening, is used for separating an ink inflow side from an ink outflow side. The ink pressure in the ink-jet recording head is kept slightly negative between the ink inflow side and the ink outflow side. In addition, the amount of ink supply is proportional to the ink used in the recording head. A preferred embodiment is a valve unit that ensures that any bubbles formed in the proximity of the diaphragm valve are removed, while a negative pressure is kept in the recording head in response to minute pressure differences.
In accordance with the invention, a valve unit in an ink supply channel of an ink-jet recording apparatus includes a diaphragm valve having a thin elastic diaphragm, a valve body which is formed on surface downstream of the thin elastic diaphragm, the valve body having an opening and an elastic support portion which is attached to the valve body. The elastic thin diaphragm operates in response to pressure difference between an upstream side and a downstream side. A valve seat is positioned on the upstream side of the ink supply channel and kept in contact with the opening in the valve body. A flow-channel having a smaller sectional area is formed by: (1) a plate which is disposed on the downstream side of the valve seat, (2) the extended direction of the elastic support portion which forms the longitudinal side, and (3) the end portion side of the elastic support which forms the upward side.
The diaphragm valve has a wide area and it responds to the differences in pressure by opening the flow channel in proportion to the amount of ink used in the recording head in order to supply ink. The flow channel forming plate forms the lower region of the diaphragm valve with its lower region. Since the upward side of the plate is narrower, bubbles tend to concentrate in this section. When ink is discharged by exerting negative pressure on the recording head, the flow rate of ink in this section is prevented from unnecessarily lowering. Therefore, bubbles are carried along with the ink to the outside
Accordingly, it is an object of the invention to provide an improved valve unit for an inkjet recording apparatus.
Another object of the invention is to provide a valve unit that ensures that any bubbles formed in the proximity of the diaphragm valve are removed while a negative pressure is kept in the recording head.
A further object of the invention is to provide an improved ink cartridge which incorporates the improved valve unit and further includes an ink supply needle.
Another object of the invention is to provide an improved method for producing the valve unit.
Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification and drawings.
The invention accordingly comprises the several steps and the relation of one or more of such steps with respect to each of the others, and the article possessing the features, properties, and the relation of elements, which are exemplified in the following detailed disclosure, and the scope of the invention will be indicated in the claims.